Power amplifier module

ABSTRACT

A power amplifier module includes an amplifier that amplifies an input signal and outputs the amplified signal, a harmonic termination circuit that is disposed subsequent to the amplifier and that attenuates a harmonic component of the amplified signal, the harmonic termination circuit including at least one field effect transistor (FET), and a control circuit that controls a gate voltage of the at least one FET to adjust a capacitance value of a parasitic capacitance of the at least one FET. The control circuit adjusts the capacitance value of the parasitic capacitance of the at least one FET, and thereby a resonance frequency of the harmonic termination circuit is adjusted.

This application claims priority from Japanese Patent Application No.2016-163064 filed on Aug. 23, 2016. The content of this application isincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a power amplifier module. In a mobileterminal that uses a communication network for cellular phones, a poweramplifier module is used to amplify power of a radio frequency (RF)signal to be transmitted to a base station. In the power amplifiermodule, a harmonic termination circuit is used to attenuate a harmoniccomponent of an amplified signal that is output from an amplifier (asignal having a frequency that is an integer multiple of the fundamentalfrequency of the amplified signal). For example, Japanese UnexaminedPatent Application Publication No. 2009-302748 discloses a harmonictermination circuit that is constituted by an inductor-capacitor (LC)series resonance circuit and whose characteristics can be changed inaccordance with the signal mode.

With the recent reduction in the profile of substrates on which poweramplifier modules are mounted and increase in the frequencies of RFsignals (for example, frequencies of about 3.5 GHz or higher), thecharacteristics of a harmonic termination circuit may deteriorate due tovariations from element to element, which could be a problem. In thisregard, in the circuit disclosed in Japanese Unexamined PatentApplication Publication No. 2009-302748, the sizes of elements such asinductors and a capacitor are determined in advance and it is difficultto adjust the characteristics of the harmonic termination circuit inaccordance with the variations of the elements.

BRIEF SUMMARY

Accordingly, the present disclosure provides a power amplifier module inwhich deterioration of the characteristics of a harmonic terminationcircuit is mitigated even if variations are present from element toelement.

According to embodiments of the present disclosure, a power amplifiermodule includes an amplifier that amplifies an input signal and outputsthe amplified signal, a harmonic termination circuit that is disposedsubsequent to the amplifier and that attenuates a harmonic component ofthe amplified signal, the harmonic termination circuit including atleast one field effect transistor (FET), and a control circuit thatcontrols a gate voltage of the at least one FET to adjust a capacitancevalue of a parasitic capacitance of the at least one FET. The controlcircuit adjusts the capacitance value of the parasitic capacitance ofthe at least one FET, and thereby a resonance frequency of the harmonictermination circuit is adjusted.

According to embodiments of the present disclosure, it is possible toprovide a power amplifier module in which deterioration of thecharacteristics of a harmonic termination circuit is mitigated even ifvariations are present from element to element.

Other features, elements, characteristics and advantages of the presentdisclosure will become more apparent from the following detaileddescription of embodiments of the present disclosure with reference tothe attached drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a power amplifiermodule according to a first embodiment of the present disclosure:

FIG. 2 is a diagram illustrating an equivalent circuit of a harmonictermination circuit in the power amplifier module illustrated in FIG. 1;

FIG. 3 is a diagram illustrating results obtained from simulation ofsignal attenuation in the harmonic termination circuit;

FIG. 4 is a diagram illustrating a configuration of a power amplifiermodule according to a modification of the first embodiment of thepresent disclosure;

FIG. 5 is a diagram illustrating results obtained from simulation ofsignal attenuation in a harmonic termination circuit in the poweramplifier module illustrated in FIG. 4;

FIG. 6 is a diagram illustrating a configuration of a power amplifiermodule according to a second embodiment of the present disclosure;

FIG. 7 is a diagram illustrating results obtained from simulation ofsignal attenuation in a harmonic termination circuit in the poweramplifier module illustrated in FIG. 6;

FIG. 8 is a diagram illustrating a configuration of a power amplifiermodule according to a modification of the second embodiment of thepresent disclosure;

FIG. 9A is a schematic diagram of an example configuration of a poweramplifier module according to an embodiment of the present disclosurewhen the power amplifier module is adjusted; and

FIG. 9B is a schematic diagram of an example configuration of the poweramplifier module according to the embodiment of the present disclosureafter the power amplifier module has been adjusted.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described with referenceto the drawings. FIG. 1 is a diagram illustrating a configuration of apower amplifier module 100A according to a first embodiment of thepresent disclosure. The power amplifier module 100A is a module thatamplifies an input signal RFin, which is a radio frequency (RF) signal,and that outputs an amplified signal RFout2. The power amplifier module100A includes, for example, an amplifier 110, a matching circuit 120A,and a control voltage generation circuit 130A. In FIG. 1, otherconstituent elements of the power amplifier module 100A (e.g., a chokeinductor, a bias circuit, etc.) are not illustrated for simplificationof illustration.

The amplifier 110 amplifies the input signal RFin and outputs anamplified signal RFout1. The amplifier 110 includes a transistor foramplification. The transistor for amplification is a bipolar transistorsuch as a heterojunction bipolar transistor (HBT), for example. Thetransistor for amplification may be a field effect transistor (FET).

The matching circuit 120A is disposed between the amplifier 110 and asubsequent circuit (e.g., a switch circuit) and matches the outputimpedance of the amplifier 110 and the input impedance of the subsequentcircuit. The amplified signal RFout1 output from the amplifier 110 isoutput as the amplified signal RFout2 via the matching circuit 120A. Thematching circuit 120A includes, for example, inductors L1 and L2, acapacitor C1, and harmonic termination circuits 140 and 150A.

The inductor L1, the inductor L2, and the capacitor C1 are connected inseries in this order. A first end of the inductor L1 is connected to anoutput terminal of the amplifier 110, and the amplified signal RFout2 isoutput from a second end of the capacitor C1. The capacitor C1 alsofunctions as a DC-cut capacitor for removing the direct-current (DC)component of the amplified signal RFout1.

The harmonic termination circuits 140 and 150A are each aninductor-capacitor (LC) series resonance circuit that includes aninductor and a capacitor. The LC series resonance circuit has a functionof attenuating frequency components near the resonance frequency. Thus,the LC series resonance circuit is designed such that the resonancefrequency coincides with a harmonic (for example, second harmonic)frequency of the input signal RFin, and thereby the harmonic componentincluded in the amplified signal RFout1 can be attenuated. For example,when the LC series resonance circuit is constituted by an inductorhaving an inductance L and a capacitor having a capacitance C, theresonance frequency f₀ is expressed by f₀=½π√LC.

The harmonic termination circuit 140 includes, for example, a capacitorC2 and an inductor L3 that are connected in series. The capacitor C2 hasa first end connected to a node between the inductor L1 and the inductorL2, and a second end connected to a first end of the inductor L3. Asecond end of the inductor L3 is grounded.

The harmonic termination circuit 150A has a structure that enables atleast one of a capacitance and an inductance of the LC series resonancecircuit to be adjusted. Specifically, for example, the harmonictermination circuit 150A includes a capacitor C3, inductors L4 and L5(first inductor), an inductor L6 (second inductor), and an FET (MN1).

The capacitor C3, the inductor L4, and the inductor L5 are connected inseries in this order. The capacitor C3 has a first end connected to anode between the inductor L2 and the capacitor C1, and a second endconnected to a first end of the inductor L4. The inductor L5 has a firstend connected to a second end of the inductor L4, and a second endgrounded (that is, supplied with a reference potential). The inductor L6is connected in parallel with the inductor L5. The inductor L6 has afirst end connected to a node between the inductor L4 and the inductorL5, and a second end connected to the drain of the FET (MN1). Theinductor L6 is an inductor for adjusting the combined inductance in theharmonic termination circuit 150A.

The FET (MN1) is an N-channel metal oxide semiconductor FET (MOSFET),for example, and has the drain, which is connected to the second end ofthe inductor L6, a gate to which a control voltage Vcont1 is suppliedfrom the control voltage generation circuit 130A, and a source grounded.The functions of the FET (MN1) will be described in detail below.

The control voltage generation circuit 130A (control circuit) generatesthe control voltage Vcont1 and supplies the control voltage Vcont1 tothe gate of the FET (MN1). The control voltage generation circuit 130Acontrols the control voltage Vcont1 as appropriate in accordance with anoffset between the resonance frequency of the harmonic terminationcircuit 150A and the harmonic frequency of the input signal RFin. Thecontrol voltage generation circuit 130A may include, for example, acontrol integrated circuit (IC) and a digital-to-analog (DA) converterand may be configured such that the DA converter generates an outputvoltage in accordance with a control signal output from the control IC.The control voltage generation circuit 130A may have any otherconfiguration.

Next, a description will be given of the function of adjusting thecapacitance and the inductance in this embodiment. An FET typically hasa parasitic capacitance between the drain and the source thereof.Specifically, the parasitic capacitance is known to be increased byincreasing the gate voltage of the FET or by increasing the gate widthor gate length of the FET. Accordingly, the parasitic capacitance of anFET can be controlled to adjust the combined capacitance in a circuitincluding the FET. In the harmonic termination circuit 150A, since thecontrol voltage Vcont1 supplied to the gate of the FET (MN1) iscontrolled, the parasitic capacitance is adjusted and the combinedcapacitance in the harmonic termination circuit 150A is adjusted.

In addition, the gate voltage of the FET (MN1) is controlled and therebythe on and off states of the FET (MN1) are switched. The conduction andnon-conduction of current through the inductor L6 connected in serieswith the FET (MN1) are also switched accordingly. Thus, the controlvoltage Vcont1 is controlled and thereby the combined inductance in theharmonic termination circuit 150A is adjusted.

FIG. 2 is a diagram illustrating an equivalent circuit of the harmonictermination circuit 150A. An FET typically includes a parasiticcapacitance and an on-resistance. Accordingly, in FIG. 2, the FET (MN1)is represented by a capacitor CT and a resistance element RT that areconnected in parallel. The elements illustrated in FIG. 2 are assumed tohave the following impedances.

-   -   Capacitor C3: −j×(1/(ωC₃))    -   Capacitor CT: −j×(1/(ωC_(T)))    -   Inductor L4: jωL₄    -   Inductor L5: jωL₅    -   Inductor L6: jωL₆    -   Resistance element RT: R_(T)    -   Here, ω denotes the angular frequency corresponding to the        center frequency of the alternating-current signal supplied to        the harmonic termination circuit 150A. A combined impedance Z        between P1 and P2 illustrated in FIG. 2 (that is, the combined        impedance Z of the harmonic termination circuit 150A, as viewed        from a node P1 illustrated in FIG. 1) is expressed by        Equation (1) as follows.

$\begin{matrix}{Z = {\frac{( {\omega\; L_{5}} )^{2}{AR}_{T}}{R_{T}^{2} + ( {B + {\omega\; L_{5}A}} )^{2}} + {j( {\frac{{\omega^{2}L_{4}C_{3}} - 1}{\omega\; C_{3}} + \frac{\omega\;{L_{5}( {B + {\omega\; L_{5}A} + R_{T}^{2}} )}}{R_{T}^{2} + ( {B + {\omega\; L_{5}A}} )^{2}}} )}}} & (1)\end{matrix}$

In Equation (1), A=(ωC_(T)R_(T))²+1 andB=ωL₆{(ωC_(T)R_(T))²+1}−ωC_(T)R_(T) hold. In Equation (1), when theimaginary part is 0 (that is, when Equation (2) below is satisfied),ω(=ω₀) is the resonance frequency (angular frequency) of the harmonictermination circuit 150A and the resonance frequency f₀ (Hz) is given byf₀=ω₀/2π.

$\begin{matrix}{{\frac{{\omega^{2}L_{4}C_{3}} - 1}{\omega\; C_{3}} + \frac{\omega\;{L_{S}( {B + {\omega\; L_{5}A} + R_{T}^{2}} )}}{R_{T}^{2} + ( {B + {\omega\; L_{5}A}} )^{2}}} = 0} & (2)\end{matrix}$

In this embodiment, the gate voltage of the FET (MN1) is controlled andthereby the capacitance value (i.e., C_(T)) of the parasitic capacitanceand the resistance value (i.e., R_(T)) of the on-resistance vary.Specifically, as the gate voltage of the FET (MN1) increases, thecapacitance value of the parasitic capacitance increases and theresistance value of the on-resistance decreases. The on and off statesof the FET (MN1) are switched and thereby the conduction andnon-conduction of current through the inductor L6 are also switched.Accordingly, it is found from Equation (1) that the combined impedance Zvaries and the resonance frequency ω₀ of the harmonic terminationcircuit 150A can be adjusted. Specifically, if there is an offsetbetween the resonance frequency of the harmonic termination circuit 150Aand the harmonic frequency of the input signal RFin, the resonancefrequency of the harmonic termination circuit 150A can be corrected sothat the resonance frequency becomes close to the harmonic frequency ofthe input signal RFin.

With the configuration described above, the power amplifier module 100Acontrols the control voltage Vcont1 supplied to the gate of the FET(MN1) in accordance with the offset between the resonance frequency ofthe harmonic termination circuit 150A and the harmonic frequency of theinput signal RFin and can thus adjust the combined impedance Z of theharmonic termination circuit 150A and adjust the resonance frequency ofthe harmonic termination circuit 150A. Therefore, even if variations arepresent from element to element, deterioration of the characteristics ofa harmonic termination circuit is mitigated by correcting the resonancefrequency of the harmonic termination circuit.

The harmonic component to be attenuated by the harmonic terminationcircuits 140 and 150A is not limited to that of the second harmonic andmay be that of the third or higher order harmonic. The harmonictermination circuit 150A includes the inductors L4 and L5, which areconnected in series, rather than the inductor L3 in the harmonictermination circuit 140. The harmonic termination circuit 150A mayinclude a single inductor instead of the separate inductors L4 and L5.The configuration in which the inductor L3 is divided into the inductorsL4 and L5 and the inductor L6 used for adjustment is connected inparallel with only the inductor L5 can reduce the size of the inductorL6 used for adjustment.

FIG. 3 is a diagram illustrating results obtained from simulation ofsignal attenuation in the harmonic termination circuit 150A. In FIG. 3,the horizontal axis represents frequency (GHz) and the vertical axisrepresents signal attenuation (dB) in the harmonic termination circuit150A. The graph illustrated in FIG. 3 depicts how signal attenuationvaries when the gate voltage of the FET (MN1) is set to about 0.65 V,about 0.7 V, about 0.8 V, and about 1.0 V in a case where the targetvalue of the harmonic frequency to be attenuated falls within the rangeof about 1.65 to 1.81 GHz. In this simulation, the FET (MN1) has a gatelength of about 10 μm and a gate width of about 400 μm.

As illustrated in FIG. 3, it is found that the resonance frequency ofthe harmonic termination circuit 150A can be corrected to a desiredvalue by controlling the gate voltage of the FET (MN1) in the harmonictermination circuit 150A. For example, in the example illustrated inFIG. 3, when the gate voltage is about 0.8 V, the resonance frequencylies at substantially the center of the range of harmonic components andthe harmonic components in this range are substantially evenlyattenuated. By adjusting the gate voltage to, for example, about 0.8 V,therefore, deterioration of the characteristics of the harmonictermination circuit 150A can be mitigated. In this simulation, as thegate voltage increases, the resonance frequency shifts toward lowerfrequencies.

FIG. 4 is a diagram illustrating a configuration of a power amplifiermodule according to a modification of the first embodiment of thepresent disclosure. Unlike the power amplifier module 100A illustratedin FIG. 1, a power amplifier module 100B illustrated in FIG. 4 includesa matching circuit 120B in place of the matching circuit 120A, and acontrol voltage generation circuit 130B in place of the control voltagegeneration circuit 130A. The matching circuit 120B includes a harmonictermination circuit 150B in place of the harmonic termination circuit150A. In this modification and the following embodiment, portions whichare common to the first embodiment are not described and only thedifferences are described. In particular, similar operations and effectsachieved with similar configurations are not repeatedly described in theindividual embodiments.

Unlike the harmonic termination circuit 150A, the harmonic terminationcircuit 150B further includes FETs (MN2, MN3, and MN4). The FETs (MN2,MN3, and MN4) are connected in parallel with the FET (MN1). That is, theFETs (MN1, MN2, MN3, and MN4) have drains connected to the second end ofthe inductor L6, gates to which control voltages Vcont1, Vcont2, Vcont3,and Vcont4 are supplied, respectively, and sources grounded.

The control voltage generation circuit 130B generates the controlvoltages Vcont1 to Vcont4 and supplies the control voltages Vcont1 toVcont4 to the gates of the FETs (MN1 to MN4), respectively, toindividually control the respective gate voltages of the FETs (MN1 toMN4). Specifically, for example, the control voltage generation circuit130B generates either a voltage to turn on each of the FETs (MN1 to MN4)(for example, a voltage greater than or equal to a threshold voltage forthe corresponding FET) or a voltage to turn off each of the FETs (MN1 toMN4) (for example, 0 V) and outputs the generated voltage as each of thecontrol voltages Vcont1 to Vcont4. In this manner, by individuallycontrolling the respective voltage values of the control voltages Vcont1to Vcont4, the combination of the on and off states of the FETs (MN1 toMN4) can be variously changed. Thus, the combined capacitance that isthe sum of the respective parasitic capacitances of the FETs (MN1 toMN4) can be adjusted. The FETs (MN1 to MN4) may be configured to have anelement size ratio of 1:2:4:8, for example.

Also in the configuration described above, similarly to the poweramplifier module 100A, the power amplifier module 100B controls thecontrol voltages Vcont1 to Vcont4 in accordance with the offset betweenthe resonance frequency of the harmonic termination circuit 150B and theharmonic frequency of the input signal RFin and can thus adjust thecombined impedance Z of the harmonic termination circuit 150B and adjustthe resonance frequency of the harmonic termination circuit 150B.Therefore, even if variations are present from element to element,deterioration of the characteristics of a harmonic termination circuitis mitigated by correcting the resonance frequency of the harmonictermination circuit.

The harmonic termination circuit 150B may be designed such that, in aninitial state, any FET (for example, two FETs) among the plurality ofFETs is in the on state and the remaining FETs (for example, theremaining two FETs) are in the off state. The number of FETs turned onis increased when the resonance frequency is higher than the targetvalue, and the number of FETs turned on is decreased when the resonancefrequency is lower than the target value. As a result, the resonancefrequency can be corrected to either a high or low frequency.

In this embodiment, reference has been made to an example in which thecontrol voltages Vcont1 to Vcont4 are used for binary control to switchbetween the on and off states of the FETs (MN1 to MN4). However, thecontrol voltages Vcont1 to Vcont4 may have consecutive voltage values,as in the power amplifier module 100A. The number of FETs connected inparallel is not limited to four, and two, three, or more than four FETsmay be connected in parallel.

FIG. 5 is a diagram illustrating results obtained from simulation ofsignal attenuation in the harmonic termination circuit 150B. In FIG. 5,the horizontal axis represents frequency (GHz) and the vertical axisrepresents signal attenuation (dB) in the harmonic termination circuit150B. The graph illustrated in FIG. 5 depicts how signal attenuationvaries when the number of FETs turned on is changed in a case where thetarget value of the harmonic frequency to be attenuated falls within therange of about 1.65 to 1.81 GHz. In this simulation, the on and offstates of the FETs (MN1 to MN4) are not switched but the gate widths ofthe FETs are set to about 200 μm, about 300 μm, about 400 μm, and about800 μm (the gate lengths of the FETs being about 10 μm) to equivalentlyrepresent the on and off operations of the FETs.

As illustrated in FIG. 5, it is found that the resonance frequency ofthe harmonic termination circuit 150B can be corrected to a desiredvalue by changing the gate widths of the FETs (that is, by changing thenumber of FETs turned on) in the harmonic termination circuit 150B.Specifically, it is found that the larger the number of FETs turned on,the lower the resonance frequency and that the smaller the number ofFETs turned on, the higher the resonance frequency. In this simulation,when the gate width is about 400 μm, the resonance frequency lies atsubstantially the center of the range of harmonic components and theharmonic components in this range are substantially evenly attenuated.Therefore, a circuit configuration equivalent to an FET having a gatewidth of about 400 μm, for example, can mitigate deterioration of thecharacteristics of a harmonic termination circuit.

FIG. 6 is a diagram illustrating a configuration of a power amplifiermodule according to a second embodiment of the present disclosure.Unlike the power amplifier module 100A illustrated in FIG. 1, a poweramplifier module 100C illustrated in FIG. 6 includes a matching circuit120C in place of the matching circuit 120A. The matching circuit 120Cincludes a harmonic termination circuit 150C in place of the harmonictermination circuit 150A.

The harmonic termination circuit 150C has a structure that enables thecapacitance to be adjusted among the capacitance and the inductance inthe LC series resonance circuit. Specifically, the harmonic terminationcircuit 150C includes, for example, an FET (MN5) connected in parallelwith the capacitor C3. The FET (MN5) has a drain connected to the firstend of the capacitor C3, a gate to which a control voltage Vcont5 issupplied from the control voltage generation circuit 130A, and a sourceconnected to the second end of the capacitor C3.

Also in the harmonic termination circuit 150C, as in the harmonictermination circuit 150A illustrated in FIG. 1, the control voltageVcont5 to be supplied to the gate of the FET (MN5) is controlled andthereby the parasitic capacitance of the FET (MN5) is adjusted. Thus,the combined capacitance of the harmonic termination circuit 150C isadjusted and the resonance frequency of the harmonic termination circuit150C is corrected. In this embodiment, for example, when the resonancefrequency is higher than the target value, the control voltage Vcont5 isincreased to increase the parasitic capacitance of the FET (MN5). Thus,the combined capacitance of the harmonic termination circuit 150C isalso increased and thereby the resonance frequency can be decreased.Also with this configuration, the power amplifier module 100C can attaineffects similar to those of the power amplifier module 100A illustratedin FIG. 1.

FIG. 7 is a diagram illustrating results obtained from simulation ofsignal attenuation in the harmonic termination circuit 150C. In FIG. 7,the horizontal axis represents frequency (GHz) and the vertical axisrepresents signal attenuation (dB) in the harmonic termination circuit150C. The graph illustrated in FIG. 7 depicts how signal attenuationvaries when the gate voltage of the FET (MN5) is set to about 3.5 V in acase where the target value of the harmonic frequency to be attenuatedfalls within the range of about 1.65 to 1.81 GHz. In this simulation,the FET (MN5) has a gate length of about 10 μm and a gate width of about400 μm.

As illustrated in FIG. 7, it is found that the resonance frequency ofthe harmonic termination circuit 150C can be corrected by appropriatelycontrolling the gate voltage of the FET (MN5) in the harmonictermination circuit 150C. Specifically, before correction (that is, thegate voltage of the FET (MN5) is about 0 V), the resonance frequencyshifts toward the upper limit (toward about 1.81 GHz) of the harmonicfrequency to be attenuated and there is a difference in signalattenuation level in this range. On the other hand, it is found that thegate voltage of the FET (MN5) is increased to about 3.5 V, which resultsin the resonance frequency being moved to substantially the center ofthis range and the harmonic components in this range being substantiallyevenly attenuated. By adjusting the gate voltage to, for example, about3.5 V, therefore, deterioration of the characteristics of the harmonictermination circuit 150C can be mitigated.

FIG. 8 is a diagram illustrating a configuration of a power amplifiermodule according to a modification of the second embodiment of thepresent disclosure. Unlike the power amplifier module 100C illustratedin FIG. 6, a power amplifier module 100D illustrated in FIG. 8 includesa matching circuit 120D in place of the matching circuit 120C, and acontrol voltage generation circuit 130B in place of the control voltagegeneration circuit 130A. The matching circuit 120D includes a harmonictermination circuit 150D in place of the harmonic termination circuit150C.

Unlike the harmonic termination circuit 150C, the harmonic terminationcircuit 150D further includes FETs (MN6, MN7, and MN8). The FETs (MN6,MN7, and MN8) are connected in parallel with the FET (MN5). That is, theFETs (MN5, MN6, MN7, and MN8) have drains connected to the first end ofthe capacitor C3, gates to which control voltages Vcont5, Vcont6,Vcont7, and Vcont8 are supplied, respectively, and sources connected tothe second end of the capacitor C3. The functions of the FETs (MN5 toMN8) are similar to those of the FETs (MN1 to MN4) in the harmonictermination circuit 150B illustrated in FIG. 4 and are not described indetail herein.

Also in the configuration described above, similarly to the poweramplifier module 100B, the power amplifier module 100D controls thecontrol voltages Vcont5 to Vcont8 and can thus adjust the combinedimpedance Z of the harmonic termination circuit 150D and adjust theresonance frequency of the harmonic termination circuit 150D. Also withthis configuration, the power amplifier module 100D can attain effectssimilar to those of the power amplifier module 100B illustrated in FIG.4.

Next, a description will be given of an example of a method foradjusting a harmonic termination circuit in a power amplifier moduleaccording to an embodiment of the present disclosure. For example, poweramplifier modules which have been manufactured undergo inspection of thecharacteristics of harmonic termination circuits and are screened as towhether or not the characteristics of the harmonic termination circuitssatisfy predetermined criteria. Then, among the power amplifier modulesthat have been screened out since the characteristics of the harmonictermination circuits do not satisfy the predetermined criteria, a poweramplifier module for which the characteristics of the harmonictermination circuit are expected to be enhanced by adjustment of theharmonic termination circuit in the way described above is selected andthe adjustment described above is performed. As a result of theadjustment, if the characteristics of the harmonic termination circuitsatisfy the predetermined criteria, the power amplifier module isshipped or otherwise, the power amplifier module is disposed of. Inorder to prevent the adjusted characteristics from being modified due toincorrect operation after the shipment of the power amplifier module, itis desirable to disable the adjustment described above after the poweramplifier module has been shipped.

In this embodiment, for example, an element (e.g., an eFuse cell, etc.)whose output value can be changed by electronic programming is used forcontrolling the characteristics of a harmonic termination circuit. Withthe use of such an element, a state where the characteristics can beadjusted (i.e., a data rewritable state) can be changed to a state wherethe adjustment of the characteristics is disabled (i.e., a datanon-rewritable state). An eFuse cell is an element whose resistancevalue is increased by the flow of large current to thereby change anoutput value, and has a property that the output value is not restoredto the original value once the output value has been changed.Accordingly, the initial state of the eFuse cell is set to a rewritablestate and, in this state, a control voltage generated by a controlvoltage generation circuit is adjusted. Thereafter, a large current iscaused to flow through the eFuse cell to change the state of the eFusecell to a non-rewritable state. The operations described above allow thecharacteristics of the harmonic termination circuit to be keptappropriately adjusted and can prevent the adjusted characteristics frombeing modified due to incorrect operation after shipment.

Next, a description will be given of another example of the method foradjusting a harmonic termination circuit. FIG. 9A is a schematic diagramof an example configuration of a power amplifier module according to anembodiment of the present disclosure when the power amplifier module isadjusted, and FIG. 9B is a schematic diagram of an example configurationof the power amplifier module according to the embodiment of the presentdisclosure after the power amplifier module has been adjusted. Asillustrated in FIGS. 9A and 9B, a power amplifier module 1000 accordingto an embodiment of the present disclosure includes a control terminalT1. The power amplifier module 1000 is placed on a screening jig 200 forinspection after manufacturing. At this time, a voltage of apredetermined level is supplied to the control terminal T1 from theoutside via a connector 202 (see FIG. 9A). The power amplifier module1000 can be configured such that the characteristics of a harmonictermination circuit can be adjusted only within a period during whichthe voltage of the predetermined level is supplied to the controlterminal T1 from the outside. Thus, when the power amplifier module 1000is located on the screening jig 200, a writing operation can beperformed on the power amplifier module 1000 to adjust thecharacteristics of the harmonic termination circuit. After thecompletion of the adjustment for the harmonic termination circuit, thepower amplifier module 1000 is mounted on a motherboard 300 in a productto be shipped. At this time, for example, ground potential is suppliedto the control terminal T1 (see FIG. 9B). Thus, the writing operation isdisabled while the power amplifier module 1000 is mounted on themotherboard 300. This configuration can also prevent the adjustedcharacteristics from being modified due to incorrect operation after theshipment of the power amplifier module. In this configuration, incorrectoperation is prevented without necessarily the use of the eFuse celldescribed above and a smaller number of components are thus used. Inaddition, it is no longer necessary to take time to perform a writingoperation on the eFuse cell. The adjustment method for a power amplifiermodule is not limited to the methods described above.

Exemplary embodiments of the present disclosure have been described.Each of the power amplifier modules 100A to 100D includes thecorresponding one of the harmonic termination circuits 150A to 150D,each including one or more FETs, and the corresponding one of thecontrol voltage generation circuits 130A and 130B for controlling thegate voltage of the one or more FETs, and the capacitance value of theparasitic capacitance of the one or more FETs is adjusted and can thusadjust the resonance frequency of each of the harmonic terminationcircuits 150A to 150D. Therefore, even if variations are present fromelement to element, deterioration of the characteristics of a harmonictermination circuit is mitigated by correcting the resonance frequencyof the harmonic termination circuit.

In the power amplifier modules 100A and 100B, the harmonic terminationcircuits 150A and 150B each include the capacitor C3 and the inductorsL4 and L5, which are connected in series, the inductor L6, which isconnected in parallel with the inductor L5, and the FET (MN1), which isconnected in series with the inductor L6. By controlling the controlvoltage Vcont1, it is possible to adjust the parasitic capacitance andthe resistance value of the on-resistance of the FET (MN1) and to switchbetween the conduction and non-conduction of current through theinductor L6. Thus, the combined impedance Z of each of the harmonictermination circuits 150A and 150B can be adjusted and the resonancefrequency can be corrected.

In the power amplifier module 100B, the harmonic termination circuit150B includes the FETs (MN1 to MN4), which are connected in parallel,and the control voltage generation circuit 130B individually controlsthe respective gate voltages of the FETs (MN1 to MN4). Thus, thecombination of the on and off states of the FETs (MN1 to MN4) can bevariously changed. Accordingly, the combined impedance Z of the harmonictermination circuit 150B can be adjusted and the resonance frequency canbe corrected.

In the power amplifier modules 100C and 100D, the harmonic terminationcircuits 150C and 150D each include the capacitor C3 and the inductorL4, which are connected in series, and the FET (MN5), which is connectedin parallel with the capacitor C3. By controlling the control voltageVcont5, it is possible to adjust the parasitic capacitance and theresistance value of the on-resistance of the FET (MN5). Thus, thecombined impedance Z of each of the harmonic termination circuits 150Cand 150D can be adjusted and the resonance frequency can be corrected.

In the power amplifier module 100D, the harmonic termination circuit150D includes the FETs (MN5 to MN8), which are connected in parallel,and the control voltage generation circuit 130B individually controlsthe respective gate voltages of the FETs (MN5 to MN8). Thus, thecombination of the on and off states of the FETs (MN5 to MN8) can bevariously changed. Accordingly, the combined impedance Z of the harmonictermination circuit 150B can be adjusted and the resonance frequency canbe corrected.

In the harmonic termination circuits 150A to 150D, by way of example, anFET is connected in parallel with either an inductor or a capacitor.Each of the harmonic termination circuits 150A to 150D may include bothan FET connected in parallel with an inductor and an FET connected inparallel with a capacitor. For example, if the resonance frequencyshifts toward higher frequencies, the FET connected in parallel with thecapacitor may be adjusted to correct the resonance frequency to a lowerfrequency, and, if the resonance frequency shifts toward lowerfrequencies, the FET connected in parallel with the inductor may beadjusted to correct the resonance frequency to a higher frequency.

Each FET included in the harmonic termination circuits 150A to 150D maybe a P-channel FET instead of an N-channel FET.

The embodiments described above are intended for easy understanding ofthe present invention, and it is not intended to construe the presentinvention in a limiting fashion. Various modifications or improvementscan be made to the present invention without departing from the gist ofthe present invention, and equivalents thereof are also included in thepresent invention. That is, the embodiments may be appropriatelymodified in design by those skilled in the art, and such modificationsalso fall within the scope of the present invention so long as themodifications include the features of the present invention. Forexample, the elements included in the embodiments and the arrangement,materials, conditions, shapes, sizes, and the like thereof are notlimited to those described in the illustrated examples but can bemodified as appropriate. In addition, the elements included in theembodiments can be combined as much as technically possible, and suchcombinations of elements also fall within the scope of the presentinvention so long as the combinations of elements include the featuresof the present invention.

While preferred embodiments of the invention have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the invention. The scope of the invention, therefore, isto be determined solely by the following claims.

What is claimed is:
 1. A power amplifier module comprising: an amplifierthat amplifies an input signal and outputs the amplified signal; aharmonic termination circuit that is disposed subsequent to theamplifier and that attenuates a harmonic component of the amplifiedsignal, the harmonic termination circuit comprising at least one fieldeffect transistor; and a control circuit configured to control a gatevoltage of the at least one field effect transistor thereby adjusting aparasitic capacitance of the at least one field effect transistor,wherein by adjusting the parasitic capacitance of the at least one fieldeffect transistor, the control circuit thereby also adjusts a resonancefrequency of the harmonic termination circuit is adjusted, wherein theharmonic termination circuit comprises a capacitor and a first inductorthat are connected in series between an output terminal of the amplifierand a reference potential, and a second inductor connected in parallelwith the first inductor, and wherein the at least one field effecttransistor is connected in series with the second inductor.
 2. The poweramplifier module according to claim 1, comprising a plurality of fieldeffect transistors, each of the plurality of field effect transistorsbeing connected in parallel with each other and in series with thesecond inductor, wherein the control circuit individually controlsrespective gate voltages of the plurality of field effect transistors.3. The power amplifier module according to claim 1, further comprising athird transistor connected in series between the capacitor and the firstinductor.
 4. The power amplifier module according to claim 2, furthercomprising a third transistor connected in series between the capacitorand the first inductor.
 5. A power amplifier module comprising: anamplifier that amplifies an input signal and outputs the amplifiedsignal; a harmonic termination circuit that is disposed subsequent tothe amplifier and that attenuates a harmonic component of the amplifiedsignal, the harmonic termination circuit comprising at least one fieldeffect transistor; and a control circuit configured to control a gatevoltage of the at least one field effect transistor thereby adjusting aparasitic capacitance of the at least one field effect transistor,wherein by adjusting the parasitic capacitance of the at least one fieldeffect transistor, the control circuit thereby also adjusts a resonancefrequency of the harmonic termination circuit is adjusted, wherein theharmonic termination circuit comprises a capacitor and a first inductorthat are connected in series between an output terminal of the amplifierand a reference potential, and wherein the at least one field effecttransistor is connected in parallel with the capacitor.
 6. The poweramplifier module according to claim 5, comprising a plurality of fieldeffect transistors, each of the plurality of field effect transistorsbeing connected in parallel with each other and the capacitor, whereinthe control circuit individually controls respective gate voltages ofthe plurality of field effect transistors.
 7. The power amplifier moduleaccording to claim 1, wherein the control circuit comprises anintegrated circuit and a digital-to-analog converter, and wherein thedigital-to-analog converter is configured to generate the gate voltageof the at least one field effect transistor in accordance with a signalfrom the integrated circuit.
 8. The power amplifier module according toclaim 5, wherein the control circuit comprises an integrated circuit anda digital-to-analog converter, and wherein the digital-to-analogconverter is configured to generate the gate voltage of the at least onefield effect transistor in accordance with a signal from the integratedcircuit.